During a field study of a forest ecosystem, ecologists monitor the decomposition of leaf litter. Over several weeks, they record a significant decrease in organic nitrogen in the litter, a corresponding increase in soil ammonium ions (NH4+\text{NH}_4^+NH4+), and a rise in soil temperature due to metabolic heat release.
Which of the following correctly describes the organisms responsible for this stage of the nutrient cycle, their method of nutrition, and the metabolic reaction that causes the temperature rise?
Saprobionts performing extracellular digestion; the temperature rise is due to exothermic respiration.
Nitrifying bacteria performing intracellular digestion; the temperature rise is due to exothermic nitrification.
Saprobionts performing intracellular digestion; the temperature rise is due to endothermic respiration.
Denitrifying bacteria performing extracellular digestion; the temperature rise is due to endothermic denitrification.
